Vernier motor



Jan. 24, 1933. l.. w. CHUBB 1,894,979

VERNIER MOTOR Filed Aug. 26, 19:51 2 sheets-sheet 1 WITNEssE's: sNvENToReM- womb.

Jah. 24, 1933. w, CHUBB 1,894,979

' VERNIER MOTOR Filed Aug. 26. 1931 2 Sheets-Sheet 2 INVENTOR PatentedJaa. 24,1933

'UNITED s'rATEsPATsNr OFFICE LEWIS -W. CHUBB, OF PITTSBURGH.PENNSYLVANIA, ABBIGNOB T WESTINGHUSLI ELECTRIC MANUFACTURING COMPANY, ACORPORATION OF PENNSYLVANIA VEBNIEB KOTOR Application illed August 86,1831. Serial No. 559,401.

My invention relates 'to a vernier motor for use either as a low-speedsynchronous motor for clocks, phonographs, or the like, or as a magnetic4reduction-gear u'nit for driving clocks, speeclometers, submarines, or,in fact whenever a reduction gear is needed.

The object. of my invention is to provide a simple and economical motorof the form descri ed, 'the' same being embodied either as aself-starting motor or as a non-self-starting motor.

In the accompanying drawings,

Figure 1 is a plan view of a synchronous clock motor embodying myinvention,

Figs. 2 and 3 are plan and longitudinal sectional views, respectivel ofa magnetic reduc-ing gear unit em ying my invention,

Fig. 4 is a fragment-ary plan view of a cascade vernier motorforeffecting a double reduction in speed, as compared to the fullsynchronous speedof a two-pole motor,

Fig. 5 is a vertical section of a phonograph motor embodying myinvention,

Fig. 6-is a plan view of the motor shown in Fig. 5, and l Fig. 7 is aplan view of a multipolar svnchronous clock motor, with parts brokenaway to show the construction.

Fig. 1 shows a stator 8 wound as a splitphase Gramme ring, the samehaving a twopole winding 9, with a two-phase supply shown as beingobtained by capacitors 10 in series with one of the phases of thewinding 9. the whole being supplied from a single.

phase source 11. The inside surface of the stator core 12 has thirtyteeth 13. Cooperating with the statormember 8 is a rotor membercomprising a magnetic core 14 without winlling and having, in this case,thirty-two teet On a (S0-cycle supply, the stator windingA willproduces. rotating field making 8600 revolutions perminute. It will benoted that the teeth at the top and bottom of Fig. 1 are coincident.whereas those at lthe right and lef?. are displaced approximatelyone-half of a. tooth pitch. In the vertical positions, the radial gaplreluctance will be low, and at the-sides it will be high. .As the'eldrevolves, there lwill be a tendency for the coincidence of teeth torevolve with the field. In Fig. 1, this will mean that, for eachrevolution of the sta-tor field, the rotor will move in the samedirection, two complete rotor tooth-pitches. In the motor shown in Fig.1, therefore, the rotor will turn at 225 revolutions per minute, and itwill remain locked at this speed as a synchronous motor.

In Figs. 2 and 3 I have illustrated my invention as a ma etic reducinggear. This embodiment of t e invention involves three relatively movingparts, any one of which may be held stationary, whereupon the other twoarts will take up their definite s eeds relative to the stationary part.In or er to fix our ideas, and to facilitate the description, I shallassume that a motor or rime mover of some kind is driving a pul ey-orgear 16 which is fixed to a shaft 17 carrying a two-pole magnet 18 whichmay be either an electromagnet (of any number of poles) or,

as shown, a permanent magnet. This magnet may be either on the outside,or, as shown, on the inside, as the rotor of a synchronous motor.

Surrounding themagnet 18 in Figs. 2 and 3 are two concentric spacedcylinders 19 and 2O of spaced, axially-extending magnetic poles or teeth21, which may be conveniently formed by bending' the teeth over from twomagnetic disks 22 and 23, respectively. The shaft 17 of the permanentmagnet rotor 18 is journalled in these disks 22 and '23.

The two disks 22 and 23 are shown as each having a (pulley or gear wheelattached thereto, as in icated at 24 and 25, respectivel Ordinarily, oneof these members will be he d against rotation, as byl means of a brakeband 26 on the pulley 25, whereupon the other pulley 24 will rotate at adefinite speed, depending upon the speed of the rotatin magnet 18 andthe relative numbers of teet 19 land 20, as will now be described.

The teeth 19 and. 20 of the magnetic reducing gear shown in Figs. 2 and3 are designed upon the same vernier princi le which is characteristicof all of the embodiments of 'my present invention. In a two-poleconstruction, as shown, the stator member will 100 have two teeth moreor less than the rotor member. In Figs. 2 and 3 the rotor member 19 isshown as havin thirt teeth, whereas the stator member 20 as thirty-twoteeth. As the magnetic field 18 rotates, the coincidence of teeth willfollow the field, but 'since the rotor. has less teeth than the stator,its rotation will be in the direction opposite to the rotation ofthefield. If the two-pole field member 18 rotates at 3600 revolutions perminute, the rotor member 19 will rotate ackwardly at a synchronousspeed'of 240 revolutions per minute.

If the member 19 were held stationary and the member 20 permitted torotate, While the twoole field member still rotates at 3600 revo utionsper minute, the rotating member 20 would rotate in the same direction asthe tield at xeeoo=225 R.. P.I M.

'slow-speed rotor or driven member may be either forward or backward,according as the rotor has two teeth' more or two teethless than thestator teeth. The speed of rotation is determined by the number of rotorteeth.

It will be understood that the embodiments of my invention shown iii thedrawings are intended more to show the principles of t einvention ratherthan the specific design. In the reducn Agear embodiment shown in Fig.3, it is desirable that the inner cylindrical member 19, which isclosest to the permanent magnet 18, shall be composed oteeth 21which-are magnetically insulated from each other, as well as poible, sothat the flux from the ends of the rmanent magnet 18 will pass directlythroug the teeth 21 of the innei cylinder-19, acro 'the two air gaps, tothe teeth 21 of the outer c linder 20, whereupon the flux is returned mthe' north pole to the south pole, through the magnetic disk-like yoke23 of the cuter cylinder 20. To this end, the disk 22 ofthe innercylinder 19 is cut away, in ider formation, as indicated at 267, so asto eave as small a rim 27 as possible, thereb limiting the shuntin of te magnetic flux. t will be understoo of course, that the spider part 26of' the oke 22 may be made of non-ma etic materia with the magneticteeth or ins 21, constituting the cylindrical member 9, suitably securedthereto..

If avery great speed-reduction.. is necessary, this may beobtainedeither with a very large numberof teeth, or by cascading the verniersystem already described. As an example of' a cascade arrangement, Fig.4 shows a stator core 30 suitably wound with a twofpole, two-phasewinding 31 for producin the ing, sa a clockwise field rotatiingiat 3300R. There are two rotor members,- an intermediate annular rotor core 32disposed within the stator core 30 and separated therefrom by an air ga33;-andan inner rotor member 34 dispose within the intermediate annularmember -32 and .separated therefrom by an air gap 35.

As an example, the inner periphery of the stator core 30 is providedwith one hundred 120 X3600=6O R. P. M.

and the speed of the inner rotor 34 will be It will be noted that theii'iner rotor 34 rotates backwardly with respect to the inter- 4mediaterotor, at one-sixtieth of the speed of the rotating flux in theintermediate rotor, and since the intermediate rotor is rotatingforwardly at a speed` of 60 R. P. M. with respect tothe' stator flux,the speed of rotation of the flux, with respect to the intermef diatemember is 3600 60=3540 R.-4 P. M. Since the inner rotor member 34rotates backwardly with res ect to the intermediate meinber 32 at 59 R.M. 'andsince the intermediate member rotates forwardly 4at 60 R. P. M.,the actual rotation of the inner rotor 34 will, therefore, be onerevolution per minute ositive or forward direction. It is thus evidentthat the second hand of a clock can be directly connected to theinnerrotor 34. The minute and hour hands may be geared to the rotor 34,either by ordinary gearing, 'or by vernier magnetic reduction gearing,as will be readily understood..

Figs. 5 and 6 show my invention as a means for driving the turn-table 41f aphonograph. Thus the bottom of the turn-table carries the rotormember 42 of one of my vemier motors, having 92 teeth, thereby fixingthe speed of rotation of the rotor member at 43 has a number o teethwhichis less than the rotor teeth, the difference being equal to .twotimes the number of pairs of statorpoles.

For a two-pole stator, the stator poles would be ninety.' For afour-pole st ator, as shown,

the number of stator llsiseighty-eight.

Fig. 7 shows an ein A iment of my inven,

than the number of stator poles tion in a shaded-pole singlehase motorhavsix stator poles, each 'vided into live po e pieces or teeth, makingthirty stator teethj in all.A The rotor member 46 has thirt -sixteeth'47, thus .advancing the rotor mem er by six rotor teeth, orone-half of a revolution for eachcomplete'rotation of the stator field,which requires three cycles because there lare three pairs of statorteeth. The rotor, therefore, rotates synchronously at 200 R..P. M. on acyc1e supply. As shown by the broken-away portions in Fig. 7, abouthalf' of the stator teeth, or three teeth of each pole, are shaded bymeans of a shading ring 48, so as to lproduce the eii'ect Iof asplit-phase or rotating field, in a manner which is well known. e

It is not possible to make the difference between the stator teeth andthe rotor teeth less because it is necessary to have tooth coincidenceunder both a north pole and a south pole simultaneously, so that therewillbe a' good return path for the flux. It is possible to make thedifference between the stator teeth and the rotor teeth an exactmultiple of'the stator teeth, but this would have the elect ofproportionately reducing thespeed-reduction, or proportionatelyincreasing the speed of the low-speed rotor, so that there would normallbe no object in u sin adiierence which is larger than the num erofstator poles.

When the number of rotor teeth exceeds the number of stator teeth2 theprogression of toothcoincidence-will bein the same direcf tion as therotation of the stator field, so that thel motor will bereadilyself-starting by reason of hysteresis and eddy currentsin' the rotormember, either one of which may be increased at will, the former bychoosing an iron or iron alloy having alarge hysteresis loss or highremanence, and the later by uti- 'lizing' a disk of conducting materialor a squirrel-cage wind'in or the like. The starting torque of theseorwardly rotating vernier motors may also be increased by increas, ingthe effectiveness of the damping ring 48, in the split-pole motor shownin Fig. 7.

For vernier motors' which rotate backwardly, self-starting can beobtained only by reducing the hysteresis and eddy-current torques to aminimum, because these torques are in opposition to the direction ofprogression of tooth-coincidences. In such motors,

it is desirable to reduce the inertia ofthe rotor.member toas Iowavalue. as possible and also to reduce its synchronous speed b increasingthe number of rotor teeth if-sel starting characteristics are to beobtained. In general, my backwardly rotating Avernier motors will not beself-starting.

In'the case of my so-called magnetic reducing gear, in .which apermanentmagnet is rotated, self-startin is always easy regardless of thedirection -of rotation, both because of the nature of the rotat' fieldand because the slow-speed driven e ement of my magnetic reducing gearstarts up at the same time as the rotating permanent ma et.

, general, my vernier motor will operate if a few of the teeth of eitherthe stator member or the rotor member, or both, are missin". The onlrequirement is that the tooth pitclli of the c osely-spaced teeth shallbe uniform and equal to 360/T, where T is the number of teeth that themember would have if no teeth were missing. The operation is the same asif all T teeth were present, except for a slightly reduced torque.

In my cascaded motor, when it is necessary for the twospeed-reductionsto be in the same ratio, so-that the intermediate rotormember 32 (Fig. 4) has more teeth on its inner periphery than its' outerperiphery, it is desirable to have as little iron as possible betweenthese two sets of teeth, so that not much of the flux will flowcircumferentially through th iron. If the inner and 'outer teeth are theny, to make the rotor speed -approximately 78.

Thus

..T,=2-)v approximately.

While I have shown my invention in several forms of embodiment, and havesuggested several uses thereof, I desire it to be understood that myinvention is not limited to such embodiments or uses. I desire, there-Vmeans for producing a rotating magneticA field therein, characterized bythe tooth pitches 'of .the stator and rotor members being different, andcorresponding to total -tooth numbers T. and Tr for the stator androtor, such that 360/T. and 360/T, are the stator and rotortooth-pitches, in degrees, and T.Tr= :tn-p, exactlv, where p is thenumber of poles 'of the rotating field, and n is any small integerexcept zero, the actual numbers of stator and rotor teeth being both atleast several times said difference :t T.- Tf).

2. The invention as set forth in claim 1, characterized bv thespacesbetween anv successive teeth being larger than a single airgapbetween the rotor and stator members.

3. The invention as set forth in claim 1. characterized b v the factthat the teeth of means for at least one of said members are alluniformly spaced and extend around the entire periphery.

4. A vernier motor comprising toothed stator and rotor members, eachmember having uniformly s )aced maenetizable teeth extending arouni theentire periphery, and

iroducing a rotatin field, threading throu h coincic ing statorandrotor-member teet i, from one member to the other, and back againthrough other coinciding teeth, the coincidence of the fiuxcarryingteeth progressing slowly around the periphery, by Vernier action, as thefield rotates, characterized by the diti'erence between the numbers ofthe stator teeth and the rotor teeth being exactly equal to iup, where pis the number of )oles of the rotating field, and n is any-smali integerexcept zero, the numbers of stator and rotor teeth being both at leastseveral times said difference.

5. The invention as set forth in claim 4, characterized by the spacesbetween successive teeth being larger than a single air-gap between therotor and stator members.

6. A vernier motor comprising toothed stator and rotor members, eachmember having uniformly spaced ma netizable teeth extending'around theentire periphery, and

means for (producing a.- rotatin magnetic field, threa ing throughcoinci ing statorand rotor-member teeth, from one member to the other,and back again through other coinciding teeth, the coincidence of thefluxcarrying teeth progressin slowly around the periphery, by Vernieraction, as the field rotates, characterized by the di'erence between thenumbers of the stator teeth and the rotor teeth being exactly equal toip, ,where p is the number of poles of the rotatin field, the numbers ofstator and rotor teeth eing .both at least several times said diierence.

7. The invention as set forth in claim 6, characterized by the spacesbetween successive teeth being larger than a single air-gap between therotor and stator members.

8. A vernier motor comprising toothed 'stator and rotor members, eachmember having uniformly spaced ma netizable teeth ex-` Aback againthrough other coinciding teeth,

the coincidence of the flux-carrying teeth progressing slowly around theperiphery, by vernier action, as the field rotates, characterized by thedifference between the numbers of the stator teeth and the rotor teethbeing exactly equal to .-tp, where poles of the rotating fiel the-numbers of magnetic g is the number of' stator and rotor teeth beingboth eral times said difference.

9. A self-starting vernier motor comprising toothed stator and rotormembers, each member having uniformly s aced magnetizable teeth extendinaroun the entire periphery, and a win( ing on the stator member forproducing a rotating maenetic field, when energized from acounnercia'-frequency power circuit, said rotating magnetic fieldthreading through coinciding stntorand rotor-member teeth, from onemember to the other, and back again through other coinciding teeththe-coincidence of the fiuxcarrying teeth progressing slowly around theperiphery, by vernier action, as the field rotates, characterized by thedifference between the numbers of the stator teeth and the rotor teethbeing exactly equal to ip, wherep is the number of poles of the rotatingfield, the numbers of stator and rotor teeth being both at least severaltimes said difference, the spaces between successive teeth being largerat least sevthan a single air-gap between the rotor and ing uniformlyspaced magnetizable teeth n extending around the entire periphery, and athird member rotatabl f Vmounted concentrically in operative relation tosaid stator and rotor members, said third member being a salient-polefield member for producing a rotating magnetic field, when rotated, saidrotating magnetic field threading through coincidingstatorandrotor-member teeth, from one member to the other, and back .againthrough other coinciding teeth, .the coincidence of theI flux-carryingteeth progressing slowly around the periphery, by.l vernier action,asthe field rotates, characterized by the difference betweenthe numbersof the stator teeth and the rotor teeth being exactly equal to ip, wherep is the number of poles ofthe rotatin field, the numbers of stator androtor teet being both at least several times said difference.

11. A. vernier motor comprising toothed stator and rotor members, eachmember havingl uniformly spaced magnetizable teeth4 extending around theentire periphery, and a third member rotatably mounted concentrically inoperative relation to said stator and rotor members, said third memberbeing a salientole permanently-ma etized field member or producin arotating magnetic field, 'when rotated, said rotating magnetic fieldthreading through coinciding statorand rotor-member teeth, from onemember to the other, and back again through other coinciding teeth, thecoincidenceof the fluxcarrying teeth progressing slowly around theperiphery by vernier action, as the field rotates, characterized by thedi 'erence between the numbers of the stator teeth and the rotorteethbeing exactly ual to ip, where p is the number of poles o the rotatinfield the l numbers of stator and rotor teeth eing both at least severaltimes said difference.

12. A magnetic reducing ar comprising a double-air ap motor having arotating magnet mem r, a stator member, and a' lowspeed rotor member,said three members being co-axial and separated by the two airgaps, saidstator member and said low-speed rotor member havin a large number ofmagnetic teeth, the teet i of the member nearest saidV rotatin magnetmember being sufficientl we insulated magnetically from each ot er to beable to transmit a material portion of the flux on through to the othertoothed member, the difference between the numbers of teeth inl the twotoothed members being equal to the number of poles of the field of therotatin magnet member.

13. A cascaded ouble-airga vernier motor comprising a stator memberaving a large number of magnetizable teeth, means for producing arotating magnetic flux to pass through successive teeth of said statormember, and two multitoothed rotor members op- 4eratively'associatedwith said stator member,

said three members being co-axial andseparated by the two airgaps, theintermediate member being one'of the rotor members and having inwardlyand outwardly .projectin magnetic teeth suftcientl well insulatemagnetically from each ot er tobe able to transmit a material portion ofthe flux on through to the other rotor member, the difference betweenthe number of teeth on 'opposite sides of oue air ap being and thedifference between t e number o teeth on opposite sides of the other gapbeing p, where is thenumber of oles of the rotating flux, t e same'being a re atively small number,

14. A self-starting vernier motor having a sta-tor member wound forenergization from a single-phase commercial-frequency source, means forproducing a rotation of the field in said stator member, said statorwinding being wound on a magnetizable core having a large number ofteeth T., and a rotor member operatively associated with said statormember and connected to .the turntable` shaft underneath the turntable,said rotor member comprising a magnetizable core having a lar e numberof teeth T,', characterized by the act'that T, and TI are'integralnumbers such that T=20f/13, approximately, and T.=-T.+p,

where f is the frequency and p is the number of stator oles.

15. A s ow-speed synchronous motor operating on a commercial-frequencysinfflephase supply, comprising a magnetiza le stator core having'alarge number of teeth uniformly distributed about its air-gaplperiphery,a magnetizable rotor core having a arge number of teeth uniformlydistributed about its air-gap periphery, and means for producing atwo-pole magnetic field rotating in said stator member at full two-polesynchronous speed, the rotor member having two teeth less t an thestator member.

16 A slow-speed synchronous motor operating on a commercial-frequencysinglephase supply, comprising a magnetizable stator core having a largenumber of teethu niformly distributed about its air-gap periphery, amagnetizable rotor core having a large number of teeth uniformlydistributed -about its air-gap periphery, and means for producing atwo-pole magnetic field rotating in said stator member at full two-polesynchronous speed, the rotor member having two teeth more than thestator member.

17. A slow-speed synchronous clock motor operating on acommercial-frequency singlep ase supply, comprising a magnetizzblestator'core having a large number of teeth uniformly distributed aboutits air-gap pe-l riphery, a magnetizable rotor core having a largenumber of teeth uniformly distributed about its air-gap periphery, andmeans f or producing a two-pole magnetic field rotating in said statorvmember at full two-pole synchronous s eed, the difference between thenumbers o stator and. rotor teeth being two.

In testimony whereof, I have hereuntol subscribed my name this 15th daof July 1931.

Lewis w. CHUisB.

weon/AIMER .1,894,97t?.-Lewi8 'W. Chubb Pittsburgh, Pa. 'Vnnmnn Moron.Patent dated' January 24, 1933. bisclaimer iiled' August 3, 1934, by theassignee, Westinghouaa d: Manufacturing Company.

Hereby disclaims from the scope of claims 1, 2, 3, 4, 5, 6, -7, 8, 9,and 1 7 any construction of motor in' which the numbeof rotor teeth ismore than the number of stator teeth, and hereby disclaims claim 16which reads as follows:

A slow-speed synchronous motor operating on a commercial-frequencysinglesupply, comprising a magnetizable stator core having a largenumber of teeth uniformly distributed about its air-gap periphery, amagnetizable rotor core having a large number of teeth uniformlydistributed about its air-gap periphery, and means for producing atwo-pole magnetic field rotating in said stator member at full twopoletsjnchronous speed, the rotor member havingtwo teeth more than thestator mem r. l

[oficial Game Angus: ze,l '1934.1

